Regional variation in American English speech is often described in terms of shifts, indicating which vowel sounds are converging or diverging. In the U.S. South, the Southern vowel shift (SVS) and African American vowel shift (AAVS) affect not only vowels' relative positions but also their formant dynamics. Static characterizations of shifting, with a single pair of first and second formant values taken near vowels' midpoint, fail to capture this vowel-inherent spectral change, which can indicate dialect-specific diphthongization or monophthongization. Vowel-inherent spectral change is directly modeled to investigate how trajectories of front vowels /i eɪ ɪ ɛ/ differ across social groups in the 64-speaker Digital Archive of Southern Speech. Generalized additive mixed models are used to test the effects of two social factors, sex and ethnicity, on trajectory shape. All vowels studied show significant differences between men, women, African American and European American speakers. Results show strong overlap between the trajectories of /eɪ, ɛ/ particularly among European American women, consistent with the SVS, and greater vowel-inherent raising of /ɪ/ among African American speakers, indicating how that lax vowel is affected by the AAVS. Model predictions of duration additionally indicate that across groups, trajectories become more peripheral as vowel duration increases.
Southern American English is spoken in a large geographic region in the United States. Its characteristics include back-vowel fronting (e.g., in goose, foot, and goat), which has been ongoing since the mid-nineteenth century; meanwhile, the low back vowels (in lot and thought) have recently merged in some areas. We investigate these five vowels in the Digital Archive of Southern Speech, a legacy corpus of linguistic interviews with sixty-four speakers born 1886-1956. We extracted 89,367 vowel tokens and used generalized additive mixed-effects models to test for socially-driven changes to both their relative phonetic placements and the shapes of their formant trajectories. Our results reinforce previous descriptions of Southern vowels while contributing additional phonetic detail about their trajectories. Goose-fronting is a change in progress, with greatest fronting after coronal consonants. Goat is quite dynamic; it lowers and fronts in apparent time. Generally, women have more fronted realizations than men. Foot is largely monophthongal, and stable across time. Lot and thought are distinct and unmerged, occupying different regions of the vowel space. While their relative positions change across generations, all five vowels show a remarkable consistency in formant trajectory shapes across time. This study’s results reveal social and phonetic details about the back vowels of Southerners born in the late nineteenth and early twentieth centuries: goose-fronting was well underway, goat-fronting was beginning, but foot remained backed, and the low back vowels were unmerged.
Prevelar raising is the raising of TRAP and DRESS vowels before voiced velars. While BAG-and BEG-raising have been described in Canada, the Upper Midwest, and the Pacific Northwest, an in-depth investigation of their distribution across North America is lacking, especially for BEG. Using an online survey distributed to over 5,000 participants via Reddit (which skews towards younger White males) and ordinary kriging for spatial interpolation, this study finds that prevelar raising is more widespread than previously reported. BAG-raising is found in much of the North and the Upper Midwest. BEG-raising is far more variable and is common across much of the Midlands and the West, with concentrated pockets in the Northern Great Plains and various other regions. This data suggests that the two can occur independently, with areas like the upper Midwest exhibiting BAG-raising alone, and the Midlands and the West reporting BEG-raising alone. These findings suggest that additional research on prevelar raising and other infrequent phonological variables is required to uncover their regional distribution and social meaning.
In this study, pristine, single impacted and double impacted GFRP specimens were subjected to ageing by immersion in seawater at ambient temperature for different periods of time. The dominating failure mode of the aged specimens was found using acoustic emission monitoring. The water absorption capacity and flexural strength of specimen subjected to ageing were assessed to study the trend of variation. A reduction in residual strength was observed between single and double impacted specimens. Stress cycle plots from AE monitoring indicate that the onset of failure occurs sooner as the ageing time progresses. From those of impacted specimens, it can be seen that the onset of failure and damage initiation occurs sooner in double-impacted specimens than in single-impacted counterparts. Parametric peak frequency analysis shows that fiber-matrix debonding was the predominant mode of failure.
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